Gas seal



D. A. JONES Dec. 7, 1965 GAS SEAL 2 Sheets-Sheet 2 Filed Feb. 10, 1964 F/cy. 6 A/067 2% il l United States Patent 3,222,678 GAS SEAL Derrick A. Jones, Somerset Township, St. Croix County, Wis., assignor to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Feb. 10, 1964, Ser. No. 343,862 13 Claims. (Cl. 346-1) This invention relates to treating one surface of a web while exposed to at least a partial vacuum and in one aspect relates to the method and apparatus for sealing an at least partially evacuated treatment chamber while a said web is moved into and out of a partially evacuated area of said chamber.

The use ofthe electron .gun as a means for recording information onto a recording medium from an information-containing input received by said gun from a suitable source such as from a magnetic tape has become highly desirably since it enables high speed recording or high speed read-out of information fed to said gun. Since it is necessary that the electron gun operate in a partial vacuum at a pressure of between 0.1 and 10 microns of mercury, certain limitations have been imposed on the use of this electron gun for recording. The greatest limitation is imposed when the beam of electrons impinge directly upon a surface of the medium. This results because it is preferred to move the recording medium into and out of the evacuated electron gun chamber and with- ;out an adequate seal the results are unacceptable. Previously known means for moving the medium into and out of an at least partially evacuated area have required multiple chambers and considerable apparatus which tended to make such recording impractical.

The present invention however has the advantage of providing a novel means whereby the web or recording lmedium may be moved through an at least partially evacuated chamber and while in said chamber, may be subjected to treatment by the electron beam and moved out of said treatment zone without disturbing the vacuum within the treatment chamber of the electron gun.

This invention further provides a novel and comparatively simple apparatus by which a medium can be moved into and out of an area of at least partial vacuum without disturbing the vacuum and exposing :one surface of a said medium to treatment while in said evacuated area.

Several modifications of the apparatus are disclosed vherein by which direct treatment of a web may be carried out in a partial vacuum and the novel method of sealing an evacuated treatment chamber will become more apparent after a perusal of the following detailed description which refers to the accompanying drawing wherein:

FIGURE 1 is a diagrammatic view of an apparatus formed in accordance with the present invention;

FIGURE l2 is a detailed sectional view illustrating one embodiment of the apparatus;

FIGURE 3 is a bottom view of one member of the apparatus illustrated in FIGURE 2;

FIGURE 4 is a schematic view of the recording medium showing one use for the apparatus disclosed here- FIGURE 5 is a transverse sectional view taken on 4line 5 5 of FIGURE 2;

ICC

device which includes an electron gun 11 for producing an information-'containing electron beam. The electron gun includes a barrel or treatment chamber, capable of being evacuated, in which the electron beam is focused by suitable means well known in the art such as magnetic or electrostatic focusing devices. The treatment chamber is formed by suitable solid impervious members and as illustrated in FIGURE 1 comprises a cylindrical member 12 and a shoe or support member 14, the outer surface 13 of which forms an :outer terminal wall portion of the chamber. The outer surface 13 (the lower surface as viewed in FIGURE 1) of the shoe 14 denes a surface around which the web 10 travels as it is passed to and through an area exposed to the chamber for treatment of a surface thereof.

Conduit means 15 and 16 are connected to the cylindrical member 12 and to the shoe 14 and are also connected to sources of reduced pressure or means for producing at least a partial vacuum such as a pair of pumps (not shown). The conduit means 15 serves to at least partially evacuate the treatment chamber and the conduit means 16 serves to supply subatmospheric pressure to the shoe 14.

A complementary-shaped control member 17 is positioned below the shoe 14 and is mounted to be readily removed and replaced to facilitate threading the web 10 in the apparatus and around the shoe 14. The member 17 also coacts with the shoe 14 to maintain the web 10 in its path and under desired pressure conditions as will be hereinafter described.

The web 10 in the illustrated embodiments is a medium sensitive to an electron beam, for example a film or treated paper. The web 10 is provided in a supply roll 18 which is rotatably mounted on a spindle 19 as shown in FIGURE 1. The web 10` is progressively unwound lfrom the supply roll 18 and passes over a guide roller 21 and between the shoe 14 and complementary member 17 to a driven capstan 22. A resilient pressure roller 23 coacts with the capstan 22 to maintain the web 10 in frictional contacting driving engagement with the capstan to drive the web as desired. During a recording operation the capstan 22 is adapted to drive the web at a constant speed and the web is rewound upon a take-up spool 24 mounted on a driven spindle 26.

FIGS. 2, 3 .and 5 illustrate a preferred embodiment of the present invention and in this embodiment the shoe 14 .is joined with the cylindrical member 12 to form a terminal wall portion of the barrel for the electron gun or treatment chamber which is generally designated 27. An outer surface 13 of the shoe 14 is smooth to provide a low friction surface over which the web 10 may be passed, as indicated by the arrow in FIG. 2, without wrinkling. The outer surface 13 is arcuate in the lengthwise direction of the web and has a straight dimension in the transverse or widthwise direction of the web. Intermedia-te the ends of this surface 13 the shoe is formed with a slotted treatment aperture 29 communicating directly with the treatment chamber 27. The arcuate surface 13 of shoe 14-also has a relatively deep groove 31 disposed therein which surrounds the treatment aperture 29. The surface portion o1 land 30 remaining` between the groove 31 and the aperture 29 forms a sealing lip around the treatment aperture 29. As illustrated in FIG. 3 the transverse dimension of the treatment aperture 29 is less than the width of the path covered by the web 10 as indicated by the dotted lines. Portions 32 and 33 of the groove 31 extend in the lengthwise direction to the shoe 14 and join transverse portions 34 and 35 of said groove which are disposed generally parallel to the treatment and 33 are positioned outside of the path traveled by the web. A suitable passage 36 is formed in the shoe 14 and is connected with the conduit means 16 such that the groove 31 is connected to a source of subatmospheric pressure to draw at least a partial vacuum in said groove.

The complementary member 17 illustrated in FIGS. 2, 3 and 5 is formed with a generally rectangular dished-out cavity or recess 37 generally centrally thereof. The recess 37 has a transverse dimension equal to the transverse length of the groove 31 and has a lengthwise dimension slightly greater than the dimension between the anterior edge of portion 34 of the groove 31 `and the trailing edge of the portion 35 of said groove in terms of the travel of the web 10. The recess 37 thus communicates through the end po-rtions of the groove 31 with the source of subatmospheric pressure to which the passage 36 is connected such that the pressure in said recess is substantially indentlcal to the pressure in the groove 31 during operation of the apparatus.

The groove 31 forms areas of reduced pressure at the surface of the shoe 14 forwardly and rearwardly of the treatment aperture 29, in the direction of movement of the web 10, such that any gas molecules trapped between the web and the outer surface 13 of the shoe 14 are drawn away before said web crosses the land 3G and treatment aperture 29. These areas of at least a partial vacuum serve to prevent any gas from being carried into the treatment chamber 27 and thus forms at least a partial seal between said treatment chamber and the atmosphere. The partially evacuated recess 37 in the complementary member 17 serves to withdraw any gas which otherwise might reach the treatment aperture 29 and provides an equilibrium condition on the web 10 tending to negate the force on said web yand to reduce the frictional force present between the web 10 `and the surface of the shoe 14.

In operation the curved surface 13 of the shoe 14 around which the web 10 is drawn permits said web to be brought into intimate contact with the land 30 around the aperture 29 and the force placing lthe web in contact with shoe 14 may be increased by applying ya controlled braking force against the supply roll 18 by any suitable means, such that a tension is placed in the web between the capstan 22 to the supply roll 18. In this embodlment, as the web 10 is drawn across the treatment aperture 29 the electron beam 28 (see FIGURE 2) scans the exposed surface portion of the web and as the electrons strike the web, they treat the surface thereof to produce a latent or a visible image on the surface of said web as defined by the information-input to the electron gun. FIG. 4 illustrates a fragment of the web 10 as it is drawn across the treatment aperture 29 and illustrates addresses belng placed on said web.

As best illustrated in FIG. 5, the complementary member 17 has a depression extending the length of t-he member to define a guide path for the web and therefore has slight anges 38 and 39 formed along its inner and outer longitudinal edges. These flanges 38 `and 39 are spaced to receive the web therebetween and have an upper arcuate surface to conform to the arcuate configuration of the shoe 14 and in operation are contiguous to the shoe 14 .along each side thereof. Toward the mid-portion of the member 17 thev flanges are cut away defining the transverse edges of the recess 37. The height of the anges 38 and 39 is preferably only slightly greater than the thickness of the web.

The embodiment illustrated in FIGS. 6 and 7 comprises a shoe 14a formed to define the terminal end wall for a treatment chamber 27a which communicates with the outer surface 13a of the shoe 14a through a slotted treatment aperture 29a. Positioned on each side of the treatment aperture 29a are grooves 42 and 43 which have a transverse dimension greater than that of said aperture but less than the width of the web as illustrated in FIG. 7. The groove 42 is connected to a passageway 44 formed in the body of the shoe 14a and the groove `43 is connected with a passageway 45 formed in the body 'of the shoe 14a. The passageways 44 and 45 are in turn connected to an evacuating means. The groove 42 is forwardly (in the path of travel of the web) of the treatment aperture 29a and serves to draw gas molecules trapped between the web 10a and the outer surface of the shoe 14a and also tends to draw the web .against the land or outer surface portion of the shoe 14a surrounding .and defining the edges of the treatment `aperture 29a and grooves 42 and 43. T-he groove 42 serves to prevent the ingress of gas to the treatment chamber 27a from behind the web 10a and the two grooves form at least a partial seal for said treatment chamber. A complementary member 17a is formed with a dished-out portion or recess 46 in its upper surface in a position opposite to the grooves 42 and 43 and the treatment aperture 29a as show-n in FIGURE 6. However, in this embodiment the recess 46 is c-onnected by suitable passage means 47 to a source of subatmospheric pressure (not shown) such that a pressure may be drawn in the recess 46 which is equal to or higher than the pressure drawn in the grooves 42 and 43. With this embodiment the pressure in the recess 46 is generally slightly higher than the pressure in the grooves 42 and 43 thus the pressure i-n lthe recess 46 places a force against the web 10a to place the same in intimate contact with the surface surrounding the treatment aperture 29a as the web is moved thereacross. With this modification a greater number of pumps or sources of subatmospheric pressure `are required but it is not necessary to place a braking force on the supply roll as the web is progressively drawn off said roll.

The web 10a which is usable with this embodiment of the invention preferably has a relatively high tensile strength, since the friction between the web and the shoe may be somewhat greater than that illustrated in the embodiment of FIGURES 2, 3 and 5 and it is preferable that the web be impermeable to result in the best seal for the treatment chamber.

In the embodiment of FIGURES 6 and 7 the complementary member 17a is formed with a depressed central portion which extends the length of said member and defines a guide path for the web 10a. The depression is of a width to allow suitable clearance for free movement of the web 10a therethrough. The flanges formed on the inner `and outer edge portions conform to the surface of the shoe 14a and the member 17a is positioned contiguous to the shoe 14a by suitable means not shown.

The embodiment of FIGURE 8 includes a shoe 14b having a generally planar outer surface over which the web 10b is moved anda complementary member 17b having 4a similar complementary surface to cooperate therewith. A pair of transverse grooves 51 and 52, having dimensions larger than a treatment aperture 29b, are formed in ythe body of the shoe 14b and are connected to passage means which are in turn connected to pumps for drawing .a partial vacuum therein. A recess 53 formed in the member 17b is connected to an independent means for drawing a partial vacuum in the recess 53 but in this modification the pressure in this recess is controlled to be always somewhat higher than the pressure in the Vgrooves 51 and 52 to afford a force against the web 10b placing said web in intimate contact with the surface of the shoe 14b in the area surrounding the treatment aperture 29h formed in said shoe and communicating with a treatment chamber 27b.

In the structu-res illustrated and described above the webs 10, 10a and 10b are progressively passed through an area of at least partial vacuum and While in said area the v.portion of'said web which crosses the treatment aperture is exposed to the treating chamber to be treated. This provides for the direct impingement of electrons from the electron beam onto the surface of the web and the web lserves to seal the terminal wall of the treatment chamber as the same is moved over the aperture. It will be seen however that this app-aratus and method may have utility in numerous operations other than the recording application disclosed.

Having thus described my invention all changes and modifications in the illustrated structure are contemplated which may fall within the scope of the appended claims.

What is claimed is:

1. A process of treating one surface of a web in the presence of at least a partial Vacuum which comprises drawing at least a partial vacuum on an enclosed treating chamber having a relatively narrow elongate treatment aperture therein,

continuously passing said web across a smooth sealing lip which surrounds said aperture,

drawing at least a partial vacuum on the surface of said web which is to be treated through a second aperture adjacent to said sealing lip and separate from the treatment aperture thereby creating a seal between said treatment aperture and the atmosphere by means of said web, and

treating the portion of said web which crosses said treatment aperture and is exposed to said treating chamber. 2. The process of treating one surface of a web while the same is exposed to a treatment chamber which is at least partially evacuated comprising progressively passing the web across an outer smooth surface portion o-f an evacuated treatment chamber which portion is formed with a treatment aperture communicating with the interior of said chamber,

drawing at least a partial vacuum to the surface of the web which is to be treated before said surface crosses said treatment aperture by means of an aperture in said surface portion separate from the treatment aperture and on which a different partial vacuum is drawn to bring said web toward said surface portion of said chamber to provide at least a partial gas seal between said chamber and the atmosphere,

placing another force upon said web which will place said web in intimate contact with said surface portion as the web passes thereover and over said aperture to restrict gas from entering said aperture as said web is moved thereacross, and

treating the portion of said web which crosses said treatment aperture .and is exposed to said vtreatment chamber.

3. The process described in claim 2 wherein said outer surface portion of said chamber is arcuate in the lengthwise direction of movement of the web and is straight in the widthwise direction of movement of the web and tension is applied to said web as it passes across said treatment aperture placing the web in intimate contact with said outer surface portion.

4. The process described in claim 2^wherein said web is passed between said outer surface portion `of said chamber and a contiguous complementary-shaped `surface member having a recessed area adjacent said treatment aperture, and controlled uid pressure is applied thereby against the side 'of said web opposite said treatment aperture to force said web toward said surface portion as said web crosses said treatment aperture.

5. The process of treating one surface of a web in the presence of a partial vacuum comprising drawing at least a partial vacuum upon a treatment chamber having a treatment aperture therein communicating with a smooth outer surface of said chamber which has a smooth land surrounding said aperture,

progressively passing a web over said land and across said treatment aperture without wrinkling, drawing at least a partial vacuum on said web in an area closely adjacent each :side of said'treatment aperture by a second aperture in the chamber separate from said treatment aperture by apertures in said outer surface separate from said treatment aperture and in the path of travel-of said web to form a seal between said chamber and the atmosphereassaid web moves across said aperture, and

bombarding the surface portion of said web which crosses said aperture with an information-containing beam to treat the exposed portion of said web.

6. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising a solid impervious support member having a surface defining a path over which a web may be drawn Without Wrinkling,

a treatment chamber capable of being evacuated, said member forming a terminal wall portion of said chamber and communicating therewith through a treatment aperture formed in said surface of said member,

means for producing at least a partial vacuum in said treatment chamber,

said surface of said support member having at least a second aperture formed therein in spaced relation with respect to said treatment aperture but in the path of movement of a said web thereacross toward said treatment aperture, and

means for producing at least a partial vacuum connected to said second aperture to draw at least a partial vacuum in said second aperture to remove gas molecules trapped between a surface of a said web and the surface of said member as a said web moves toward said treatment aperture and to subject a said web to a force tending to place the web in engagement with the surface of said member to thereby form at least a partial `seal for said treatment chamber around said treatment aperture as the web is moved across said aperture.

7. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising a treatment chamber capable -of being evacuated,

means for at least partially evacuating said treatment chamber,

support means defining a terminal wall portion of said treatment chamber and a smooth outer surface forming a path over which a web may be moved without wrinkling,

said support means having a treatment aperture formed in said surface communicating with said treatment chamber and extending generally in a widthwise direction of the path of the web and having a groove in said surface on each side of said treatment aperture and closely spaced with respect to said treatment aperture,

means for providing subatmospheric pressure connected to the grooves alfordng thereby an area of at least partial vacuum on each side of said aperture to prevent `gas from reaching said treatment aperture as a said web is moved thereacross,

a control member having a surface complementary to the outer surface of said support means and mounted in opposed relation to said outer surface yand formed with a recess in the portion thereof opposite said grooves and said treatment aperture,

said reces-s being connected to said means for providing subatmospheric pressure to control the force on a said web tending to move said web into intimate contact with said outer surface,

said grooves and recess together lwith the contiguous surfaces thus affording control for a said web to place the same in sealing relation around said treatment aperture, and

means associated with said treatment chamber for treating the surface of a said web as it is exposed to said treatment chamber.

8. Apparatus as described in claim 7 wherein said means for treating comprises an electron gun for treating the surface of a said web to impart an image thereto.

9. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising a treatment chamber capable of being evacuated,

means for at least partially evacuating said treatment chamber,

a shoe forming a terminal wall portion of said treatment :chamber and having a smooth outer surface over which a web may be moved without wrinkling, said surface being arcuate in the lengthwise direction of movement of a web and having a straight dimension in the widthwise direction of movement of a said web and being formed with a slotted treatment aperture communicating with said treatment chamber, said aperture extending in a widthwise direction and having a length less than the width of the path covered by a web,

said shoe surface being also formed with a groove surrounding said treatment aperture in closely spaced relation thereto and defining a land therebetween,

said groove being connected to means affording subatmospheric pressure and thereby serving to remove gas molecules from between a surface of a said web and said outer surface of said shoe as a said web is drawn across said land and said treatment aperture and to prevent gas from reaching said treatment aperture after said web has been drawn thereacross,

a member having a surface complementary to and contiguous to said outer surface of said shoe and having means defining a longitudinal web path, said member, being removably mounted to facilitate the threading of a web across said outer surface of the shoe and between said shoe and said member,

said member being formed with a generally rectangular recess in the portion thereof opposite said groove and said treatment aperture,

said recess communicating with said groove during operation atfording thereby a subatmospheric pressure in said recess substantially equal to the pressure in said groove for reducing the frictional force between a moving web and said outer surface,

means for transporting a said web along the path and across the surface of said shoe, and

means associated with said treatment chamber for treating the surface of a said web as it crosses said treatment aperture and is exposed to said treatment charnber.

10. Apparatus as defined in claim 9 wherein said means 11. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising a treatment chamber capable of being evacuated,

means for at least partially evacuating said treatment chamber,

a shoe forming a terminal wall portion of said treatment chamber and having a smooth outer surface over which a web may be drawn without wrinkling, said surface being arcuate in the lengthwise direction of the web and having a straight dimension in the widthwise direction of the web and being formed with a slotted treatment aperture communicating with said treatment chamber, said aperture extending in a widthwise direction and having a length less than the widthwise dimension of the path covered by a web,

the surface of said shoe being also formed with a groove on each side of said treatment aperture and positioned generally parallel and closely adjacent thereto, each said groove extending in the widthwise direction of the path covered by a said web at least as far as said aperture to define a subatmospheric pressure area in said outer surface in the path of movement of a said web across said surface forwardly and rearwardly of said treatment aperture,

5i said grooves being connected to means affording subatmospheric pressure and thereby serving to remove gas molecules from between a surface of a said web and said outer surface as a said web is drawn across said treatment aperture and to prevent gas from reaching said treatment aperture after said web has been drawn thereacross,

a member mounted adjacent said shoe and having a surface complementary to and contiguous to said outer surface of said shoe and defining a web path,

said member being formed with a generally rectangular recess in the portion thereof opposite said grooves and said aperture,

means connected to said recess affording a subatmospheric pressure therein which pressure is controlled to have a higher value than in said grooves affording thereby a resultant which forces a said web into intimate contact with the area of said shoe surrounding said treatment aperture,

means for transporting a web across the surface of said shoe and along said path, and

means associated with said treatment chamber for treating the surface of a said web as it crosses said treatment aperture and is exposed to said treatment chamber.

12. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising a treatment chamber capable of being evacuated,

means for at least partially evacuating said treatment chamber,

a shoe formng a terminal wall portion of said treatment chamber and having a smooth planar outer surface over which a web may be drawn without wrinkling,

said shoe being formed with a treatment aperture communicating between said outer surface and said treatment chamber and being formed with a groove on each side of said treatment aperture, said aperture extending in a widthwise direction and said grooves being positioned generally parallel and closely adjacent thereto to define subatmospheric pressure areas in said outer surface in the path of movement of said web forwardly and rearwardly of said treatment aperture,

means connected with said grooves to afford subatmospheric pressure therein to thereby draw a said web into intimate contact with said -outer surface and to rem-ove gas molecules from between a surface of a said web and said outer surface as a said web is drawn across said treatment aperture and to prevent gas from reaching said treatment aperture behind said web,

a member having a surface complementary to and positioned contiguous to said -outer surface of said shoe,

said member being formed with a recess in the surface portion thereof opposite said grooves and said aperture;

means connected to said recess affording subatmospheric pressure therein of a predetermined value to thereby afford means for applying an additional force on said web in the area of said treatment aperture serving to push the same into sealing engagement with said outer surface of the shoe around said aperture,

means for transporting a web across the surface of said shoe, and

means associated with said treatment chamber for treating the surface of a said web as it is exposed to said treatment chamber.

13. Apparatus for treating one surface of a web in the presence of at least a partial vacuum comprising:

member forming a terminal wall portion of said chamber and being formed with a treatment aperture extending through said member and communicating with said chamber, said treatment aperture having a widthwise dimension with respect to the 5 path over which a web is to be drawn which is less than the width of the path defined on said surface and covered by a said web,

means for continuously moving a said web over the surface of said support member and along the path dened yon the support member.

means for producing at least a partial vacuum in said treatment chamber, 10

said surface of said support member having at least a second aperture formed therein in spaced relation References Cited by the Examiner UNITED STATES PATENTS with respect to said treatment aperture but in the path amash 342%111) of movement of a said web thereacross toward said 2676868 4/1954 Jagb a an 346;5 treatment apertufe l5 2,925,312 2/1960 Hollmann 34e- 75 means for producing at least a partial vacuum con- 3 063 050 11/1964 Miu. 346 1 nected to said second aperture to draw at least a 3205301 9/1965 E his "178 "6 6 partial vacuum in said second aperture to remove tc everry gas molecules trapped between a surface of a said web and the surface of said member as a said web moves toward said treatment aperture and to sub- 0 LEYLAND M. MARTIN, Primary Examiner.

LEO SMILOW, Examiner. 

1. A PROCESS OF TREATING ONE SURFACE OF A WEB IN THE PRESENCE OF AT LEAST A PARTIAL VACUUM WHICH COMPRISES DRAWING AT LEAST A PARTIAL VACUUM ON AN ENCLOSED TREATING CHAMBER HAVING A RELATIVELY NARROW ELONGATE TREATMENT APERTURE THEREIN, CONTINUOUSLY PASSING SAID WEB ACROSS A SMOOTH SEALING LIP WHICH SURROUNDS SAID APERTURE, DRAWING AT LEAST A PARTIAL VACUUM ON THE SURFACE OF SAID WEB WHICH IS TO BE TREATED THROUGH A SECOND APERTURE ADJACENT TO SAID SEALING LIP AND SEPARATE FROM THE TREATMENT APERTURE THEREBY CREATING A SEAL BETWEEN SAID TREATMENT APERTURE AND THE ATMOSPHERE BY MEANS OF SAID WEB, AND TREATING THE PORTION OF SAID WEB WHICH CROSSES SAID TREATMENT APERTURE AND IS EXPOSED TO SAID TREATING CHAMBER. 